1. Field of Invention
This invention relates to optical micromachined or microelectromechanical system based devices with aligned structures and methods for fabricating these structures.
2. Description of Related Art
Coupling of light signals between an, optical fiber and an optical system has been a challenging issue in the design of optical systems for optical fiber communication. Strict alignment between optical fibers and optical devices, such as lenses, waveguides, photo-detectors, and the like, is needed to achieve a high coupling efficiency. For example, for single-mode fibers, alignment tolerance is normally less than 1 micron.
In particular in a micro-optoelectromechanical system (MOEMS), accurate alignment between various structures is critical to prevent undesirable optical losses. Micro-electromechanical system (MEMS) structures are normally defined on a subsrate with non-planar topography, that is, with various structures defined in different structural layers. It is difficult to achieve alignment of structures fabricated in different structural layers with an accuracy better than 1 micron. Thus, it is difficult to the alignment accuracy needed for high efficiency coupling with micro-optoelectromechanical system-based devices.
For example, for a micro-optoelectromechanical system having one or more waveguides that is to be in placed communication with an optical fiber may include a V-groove for coupling the optical fiber. The system requires a misalignment between the waveguide(s) and the V-groove of less than 1 micron to achieve high precision coupling of light signals from the optical fiber to the waveguide(s), or vice versa, to reduce optical loss.
Conventionally, alignment of waveguides and optical fibers is achieved by manual adjustment, for example, under a microscope. Such adjustment is labor intensive and costly.
The devices and methods of this invention provide high efficiency coupling between an optical fiber and an optical device.
The devices and methods of this invention separately provide accurate alignment of an optical fiber and an optical device.
The devices and methods of this invention separately provide automatic alignment of an optical fiber and an optical device.
The devices and methods of this invention separately provide alignment of an optical fiber and an optical device with reduced labor and/or cost.
This invention separately provide a micro-optoelectromechanical system-based device having an optical component accurately aligned with a coupling structure for an optical fiber.
According to various exemplary embodiments of the device of this invention, a micro-optoelectromechanical system based device with aligned structures comprises a waveguide formed in a silicon layer of the device and at least one optical fiber connection structure that is self-aligned with the at least one optical structure. In embodiments, the waveguide is formed in a silicon layer of the device. The silicon layer may be a single-crystal-silicon layer. A nitride layer may be formed on at least a portion of the waveguide.
According to various exemplary embodiments of the methods of this invention, a micro-optoelectromechanical system based device with aligned structures is fabricated by defining at least one optical structure using a masking layer and defining at least one optical fiber connection structure using the same masking layer. In embodiments, the at least one optical fiber connection structure is etched in a substrate of the device. In other embodiments, the at least one optical structure is etched in a silicon layer of the device.
According to various exemplary embodiments of the methods of this invention, a micro-optoelectromechanical system based device with aligned structures is fabricated by: providing a silicon-on-insulator wafer comprising a single-crystal-silicon layer, a substrate and an insulator layer therebetween; selectively removing a first portion of the single-crystal-silicon layer; defining at least one optical structure using a masking layer; defining at least one optical fiber connection structure using the same masking layer; selectively removing a second portion of the single-crystal-silicon layer to obtain the at least one optical structure; and selectively removing a portion of the substrate to obtain the at least one optical fiber connection structure.
In various embodiments, a layer of nitride is formed over the single-crystal-silicon layer and the substrate after selectively removing the first portion of the single-crystal-silicon layer. In various embodiments, an oxide is formed on a least the single-crystal-silicon layer after selectively removing the second portion of the single-crystal-silicon layer. The oxide is subsequently removed from the single-crystal-silicon layer.
In various embodiments, a second masking layer is formed after selectively removing the second portion of the single-crystal-silicon layer and before selectively removing the portion of the substrate. In various embodiments, a sacrificial layer is formed after selectively removing the second portion of the single-crystal-silicon layer and before forming the second masking layer. A portion of the sacrificial layer may be removed after forming the second masking layer. The second masking layer and the sacrificial layer may be removed after selectively removing the portion of the substrate.
These and other features and advantages of this invention are described in, or are apparent from, the following detailed description of various exemplary embodiments of the systems and methods according to this invention.